Gut possesses an extraneuronal mechanism for accumulating catechols from the circulation in quantitatively significant amounts. The accumulated catechols are metabolized via glucuronidation. The broad objectives of the proposal are: (1) to characterize the biochemical features of this catechol metabolizing system; (2) to assess the physiologic and pharmacologic significance of the process; (3) to demonstrate transcellular transport (serosal to mucosal side) and establish the presence of an entero-enteric circulation; and (4) to assess the role of glucuronidation in uptake and transport by this system. A variety of in vivo and in vitro techniques will be employed in the pursuit of these objectives. Studies in intact rats will be performed in order to establish the structural features which favor catechol uptake and metabolism by gut mucosa. The storage of glucuronide conjugates of catechols will be assessed in untreated intestinal mucosa after feeding a variety of naturally occurring and synthetic catechols. Transepithelial transport of catechols will be quantitated in intact rats utilizing perfused gut loops formed in situ. In studies utilizing an isolated intestinal cell preparation the metabolic and ionic factors necessary for uptake and release of catechols will be determined. The kinetics of uptake and the structure activity relationship will be explored in this system as well. In other in vitro studies, the Ussing chamber will be utilized to demonstrate net catechol transport from the serosal to the mucosal side of the gut. The role of glucuronidation will be assessed by utilizing isolated intestinal cells from Gunn rats as well as in animals in which glucuronyl transferase activity is pharmacologically altered. The long term goal of the research is a better understanding of the role of the gut in catechol metabolism and the elucidation of a major new disposal system for biologically active compounds related to the catecholamines.